1. Field of the Invention
The present invention provides a method and associated apparatus for more efficiently controlling subterranean termites by enhancing the likelihood that they will be positively attracted to the bait stations.
2. Description of the Prior Art
It has long been known that termites can enter homes and other man-made structures and cause serious damage. It has been reported in fact that termites cause more damage to wood containing buildings in the United States than any other type of insect. Most of the termite damage in the United States is caused by subterranean termites. While termites, as wood-destroying insects, play an important beneficial role in recycling and decomposition of vegetable matter, such as fallen trees, for example, into soil components, in instances where damage to or loss of buildings or other manmade structures is involved, it is critical that efficient means for limiting termite damage and, where possible, destroying termite colonies be provided.
Termites are insects in the order Isoptera. They are social insects that live in colonies and whose members have different physical characteristics and perform different functions. Termites hatch from an egg and develop through gradual metamorphosis to one of four general adult forms. The four adult forms are (a) the worker, (b) the soldier, (c) the secondary reproductives, and (d) the primary queen and king.
Workers make up the largest part of the colony. They construct and repair the termite nest, care for the eggs and young, and forage for food for the members of the colony. These are the colony members that cause damage to wood.
The soldier termite serves to protect the termite colony from attack by termite predators, such as ants, which are the principal natural termite predator. The soldier termite is conspicuous by its enlarged head and mandibles.
Numerous secondary reproductives develop in mature termite colonies. Secondary reproductives lay eggs, but the eggs develop only into worker termites as long as the primary mother queen is alive and functioning. Collectively, the secondary reproductives can produce more eggs than the mother queen.
The primary queen and king are the winged reproductives that swarm from a mature colony, fly a short distance from the nest, shed their wings, and pair off to make a chamber and start a new termite colony in a suitable substrate, such as moist soil under a tree stump or cellulose debris. It takes several years for this primary queen and king to rear a colony that is large and mature enough to produce and send out winged colonizing swarmers.
A colony of subterranean termites has requirements of protection, moisture and food. The initial female (queen) and male (king) termite will select a site which usually includes moist, partially rotted wood in contact with the soil. After establishing the site, the pair will mate and the queen will begin laying eggs. Usually, only a few eggs are laid the first few months and the queen and king will care for the young termites until the young termites are mature enough to forage for food and begin caring for the queen and king. As the queen matures, she produces more eggs. The foraging workers expand the size of the nest and construct passageways through the soil and mud-like tubes over surfaces through which they move and explore for additional sources of food. In these passageways, the termites maintain a highly humid atmosphere that is essential for their survival. Termites have a particular need for moisture and high humidity because, in comparison to most other insects, termites have a much thinner wax-like coating which is insufficient to protect them from desiccation at ambient humidity levels. For termites, moisture is more important to survival than food. For example, an entire termite colony will abandon a site that contains adequate food but that has become dry, for another site where water has been found to be more available. The termite's remarkable ability to detect an elevation of vapor pressure and move toward sources of moisture and to conserve moisture by constructing special tubes have contributed to its remarkable success throughout earth's history.
The termite colony can be considered to be an enormous amorphous organism. Like a giant amoeba, its foraging workers poke and explore in all directions from their termitaria in a continuous search for food and water for a growing population. In their constant search for food, foraging termites bite into anything softer than their hard teeth including, for example, leather, PVC pipe, and swimming pool liners.
Information related to sources of new food, threats to the colony, or damage to the nest are communicated from one termite to another by chemical odor (pheromone) communication, touch (tactile) communication, and vibrations produced by soldier termites banging their heads on the walls of the nest.
An ideal climate was created for termites when modern man developed homes and other buildings in termites' ancient homeland--the forest. In constructing homes, large numbers of huge trees were cut and removed leaving behind vast amounts of termite food in the form of tree root systems. However, as the termites depleted these food sources, they became attracted to the moisture around human home sites where lawns and ornamental plants were frequently watered, especially during dry spells. Attracted by the moisture near the foundation of the home, the foraging termites inevitably found scrap lumber, form lumber, and other cellulose debris left under and around the home by the home builder. Further foraging led the termites to the foundation wall of the home itself where numerous mortar breaks and cracks in the foundation wall provided easy access to the structure's wooden joists, framing and cellulose contents.
Older homes in established communities are particularly vulnerable to termite attack since original ornamental plants surrounding the older home have usually died and been replaced, leaving old root systems behind. In addition, leaky hose bibs and water pipes are more common in older homes than newer homes. Also, improper drainage from roofs or at the downspout outlet often directs massive amounts of rainwater along the foundation of homes. These conditions are overwhelmingly powerful attractants for termites to the site.
The best time to protect man-made structures from termite damage is during the planning and construction of the structure. Proper site location, good foundation and building design, treatment of the soil under and around the foundation, and use of treated lumber coupled with periodic inspections will protect structures for many years. Exceptionally effective protection for up to several decades was provided by the termiticide chlordane when it was used as a pretreatment in the soil under and around the foundation. However, cancellation of the registration of chlordane by the United States Environmental Protection Agency has eliminated it as a tool for protection against termites. None of the new termiticides that have replaced chlordane possess chlordane's ability to diffuse through the soil and its long residual termiticide properties.
Even the best planned and constructed buildings do come under termite attack. Termite workers are always foraging for new sources of food. Due to cracks in a building's construction material, faulty building design, or inadvertent gaps in a termiticide soil treatment due to imprecise distribution of termiticide in the soil, termites often can gain entry into a building and cause damage to the lumber therein.
After termite presence has been detected in an existing structure either by inspection, the chance notice of termite tubes or damaged wood, or the presence of swarmers in the home, there are several known means available to eliminate the termite infestation. The most often used technique is to apply chemical termiticides in the soil under the home and around the foundation. Other techniques include mechanical alteration of the building, removal of wood and other termite food sources from the vicinity, use of ventilation with vapor barriers, use of non-chemical termiticides such as nematodes, and barriers of sand of specific mesh size. In some cases, injection of a termiticide with a pressurized aerosol container into termite galleries in infested wood members, has been shown to destroy a colony of subterranean termites. However, no means of termite control as effective as chlordane has been found.
It has been known to employ bait stations in efforts to control termites. See U.S. Pat. Nos. 5,365,692 and 4,329,726.
To compensate for the limited effectiveness and/or failure of post-chlordane termiticides, termiticide researchers and manufacturers have recently developed and field tested a new means of termite control with some success. The new means of termite control is based on killing the termite colony rather than just use of a chemical termiticide barrier to block termite entry into the building. The researchers have developed termite bait stations composed of perforated, plastic tubes each containing a cellulose core. The bait stations are placed beneath the surface of the soil near the structure's foundation or on the edge of a patio or sidewalk by a licensed pest control operator. The pest control operator contracts to visit the site periodically after installation to check these bait stations for evidence of termite feeding or infestation. If termite presence is found in a bait station, the cellulose core is replaced with a new cellulose core that contains a termiticide such as a slow-acting toxicant or an insect growth regulator. See, generally, Fehrenboch, "Sentricon Colony Elimination System," Pest Control Technology, pp. 54-60, 125 (1994); Quarles, "New Technologies for Termite Control," The IPM Practitioner, Vol. XVII, No. 516, pp. 1-9 (1995); and "Sentricon: A Report from the Field," Pest Control Technology, pp. 58-60, 64 (1995).
Whether a slow-acting toxicant or an insect growth regulator is used, the termite's system of feeding one another including the reproductives distributes the termiticide throughout the colony. The slow-acting toxicant begins to exhibit its toxic effect only after the toxicant has been distributed throughout a significant portion of the colony. In the case of the insect growth regulator, the approximate ratio of 1 soldier to 10 workers is reversed. As soldiers rely on the workers to feed them, the colony starves and perishes after a few weeks.
In tests performed by Dr. Nan Y. Su and Dr. Rudy Scheffrahn at the University of Florida Research Center in Fort Lauderdale, bait stations were placed in soil around condominium buildings in areas infested with active Formosan termites. However, some of these bait stations were not found by foraging termites even though they were within 12 inches of the bait station. This is of particular interest as Formosan termites are far more aggressive than the Eastern subterranean species that flourishes in all the United States and in Canada. These scientists have concluded that subterranean termites find their food only by random probing and tubing through the soil medium. Even the manufacturers of this new baiting system have stated that the termite finds the baiting station only by chance and that there is nothing to attract the termite to the baiting station itself.
There remains, therefore, a very real and substantial need for an improved means of controlling termites in order to reduce the damage which colonies of such insects can produce to buildings and to their contents, such as wooden furniture, paper documents, books, boxes and leather shoes, for example, other human created structures, as well as materials which serve as food materials for termites, such as might be found in lumber yards. In addition, during their constant search for food and water, termites will chew through and damage non-cellulose items, such as polyvinyl chloride pipe, leather shoes, and swimming pool liners.